Applicants claim priority under 35 U.S.C. xc2xa7119 of Austrian Application No. GM 392/98 filed Jun. 12, 1998. Applicants also claim priority under 35 U.S.C. xc2xa7120 of PCT/AT99/00145 filed Jun. 8, 1999. The international application under PCT article 21(2) was not published in English.
The invention relates to a control device of the type outlined in the generic part of claim 24.
As a means of operating several tools driven by a pressurised medium. e.g. emergency cutter emergency jacks, etc., of the type used with mobile emergency and rescue equipment, hydraulic units are known which have multi-circuit pumps to supply several delivery circuits. Each tool is assigned its own delivery circuit and valves are fitted on every tool so that they can all be operated simultaneously or each individually. A device for combining fluid in construction site vehicles is known from DE 195 51 510 hereby compressed medium is uniformly applied to several actuators starting from two pumps delivering the pressurized medium via co-operating control valves and bypass lines, the intention being to improve the ability to control the working machinery. The disclosed device for combining the fluid is designed to activate four double-acting actuator units starting from two pumping units and, in the embodiment described, requires a large number of control and regulating valves and an extensive external run of lines.
Another device for regulating and activating two double-acting and one single-acting actuator starting from a pumping unit is known from U.S. Pat. No. 2,768,550 A. The objective of this invention is to provide a hydraulic system which can be supplied and controlled so as to generate different variables for several hydraulic actuator units in order to apply the compressed medium in different quantities. Again with this known device, a large number of control valves are needed in addition to bypass valves, which means that an extensive run of lines needs to be adapted to the respective configuration of the machinery, leading to a reduction in safety due installation and high costs.
Accordingly, the objective of the invention is to provide a control unit permitting optional operation of at least two work tools at the highest possible energy consumption.
This objective is achieved by the invention due to the characterising features set out in claim 24. The surprising advantage of this arrangement is that by providing a control device in the delivery circuits, a flow connection can be switched into operation as required, enabling a flow of medium to be built up in a pressure generator having a dual or multi-circuit pump and concentrated on one tool. Faster operating speeds can be achieved as a result, which shortens the usage time and significantly speeds up rescue operations. In addition, the weight of the delivery unit is of crucial importance in mobile applications and the design proposed by the invention offers a compact unit requiring few components. Since the delivery rate has a direct effect on the speed at which the tools can be operated and tools often have to be used in an alternating sequence, full use can be made of the available resources. The design proposed by the invention also eliminates connecting lines, enhancing operating safety by avoiding potential leakage and reducing assembly requirements.